Even before the coffee and espresso craze made Starbucks a household word, Americans loved their caffeine. In her book Jump-Off Creek, Molly Gloss writes of settlers in Oregon in the 1890s saving and reusing their precious coffee grounds day after day.

The proliferation of espresso stands and coffee shops across the country points to an interesting fact: caffeine is an addictive legal drug. We don't like to think of ourselves as addicts, but we are. Just try going without caffeine for one day. Your headache, irritability and fatigue will remind you that your body has become so accustomed to this drug that it can't function well without it.

Tea, coffee, espresso, cola drinks and chocolate are our favorite caffeine delivery systems. At least 80 percent of Americans consume some form of caffeine daily.

Almost everyone I know has a carefully calibrated system of getting just the right amount of caffeine each day. For me, it's one cup of strong tea in the morning. For others it may be three cups of coffee at three-hour intervals. Some sip Diet Coke all day.

At reasonable doses, caffeine has beneficial effects for most adults. It gives us energy, makes us more alert and able to focus on tasks. It creates a mild euphoric feeling by stimulating the pleasure center in the brain. This effect is similar to - but milder than - the effect of cocaine, heroin and amphetamines on the brain.

Caffeine has physical effects on the body. At higher doses, it causes the release of epinephrine which in turn causes your heart to beat faster, your blood pressure to increase and your muscles to tense up. It's a mild diuretic, meaning it increases urine output.

It is possible to overdose on caffeine. The amount needed to cause serious symptoms is different for everyone, and depends on age, weight and tolerance to caffeine. Symptoms of an overdose include: irritability, restlessness, anxiety, insomnia, rambling thoughts and speech, muscle twitching, rapid heart rate, abnormal heart beats (palpitations), flushed face, nausea and diarrhea. These symptoms are similar to those seen in people taking methamphetamine, indicating that caffeine affects the brain and body in much the same way.

Who should avoid caffeine?

• Children and teen-agers who drink caffeinated sodas instead of milk may not be getting enough calcium and other nutrients they need. Caffeine can worsen hyperactivity and affect sleep quality at a time in development when sleep is very important.

• Pregnant women, women trying to conceive and breastfeeding women should reduce their caffeine intake to the equivalent of two or fewer cups of coffee per day.

• Anyone with stomach ulcers or problems with heartburn should avoid coffee, since both regular and decaf increase stomach acid production.

• People with certain heart problems, particularly those with irregular heartbeats, should avoid caffeine.

• Women with painful, lumpy breasts (called fibrocystic breast disease) may have an improvement in symptoms if they limit caffeine intake.

• Anyone who feels anxiety or is prone to panic attacks may find that caffeine worsens their symptoms.

• Anyone who has trouble sleeping should cut down on caffeine or eliminate it completely.

If you do consume a lot of caffeine and want to cut back or stop completely, it's best to taper down slowly rather than to quit cold turkey.

Kathryn B. Brown is a family nurse practitioner with a master's degree in nursing from OHSU. Is there a health topic you would like to read about? Send your idea to kbbrown@eastoregonian.com.

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